This invention relates generally to innovations and improvements in tandem rear axle air suspensions for trucks and truck-tractors. More particularly, the invention relates to such suspensions wherein a non-reactive, roll compliant drive axle suspension having a single axle and equipped with wheel slip sensing and control means is combined with a roll stable, non-drive tag or pusher axle suspension having a single axle and equipped with means for transferring weight to the drive axle suspension. The preferred technology for the non-drive tag or pusher axle suspension is a rigid beam suspension. The wheel slip sensing and control means and the weight transfer means may be either automatically or manually operated. When the drive axle suspension is in the lead or forward position the combination is referred to as a xe2x80x9cdrive/tagxe2x80x9d suspension. When the drive axle suspension is in the rear or trailing position the combination is referred to as a xe2x80x9cdrive/pusherxe2x80x9d suspension. The term xe2x80x9cnon-reactivexe2x80x9d means that the suspension does not react appreciably to torque forces applied to a drive axle, primarily during acceleration. Being non-reactive substantially eliminates driveline torque induced problems. The term xe2x80x9croll compliantxe2x80x9d means that a suspension does not adequately resist the tendency of a vehicle to roll when negotiating sharp turns. On the other hand, a non-reactive suspension has excellent traction characteristics when encountering uneven road conditions due to its roll compliance. The term xe2x80x9croll stablexe2x80x9d means the opposite of xe2x80x9croll compliant.xe2x80x9d The term xe2x80x9cair suspensionxe2x80x9d refers to a suspension equipped with air springs or bellows for supporting a vehicle on an axle. Hydraulic cylinders with accumulators may be used as the functional equivalent of air springs.
Rear axle suspensions form important components of heavy duty, over-the-road trucks and truck-tractors, with respect to the operating characteristics, original costs and maintenance of such vehicles. Accordingly, it is desirable to provide such rear axle suspensions which have optimum operating characteristics combined with minimum weight and costs of production and maintenance. It has been found in accordance with the present invention that such objectives can be achieved by providing tandem rear axle air suspensions which combine a non-reactive, roll compliant drive axle suspension having a single axle with a roll stable, non-drive tag or pusher axle suspension having a single axle of the rigid beam type. Preferably, the drive axle suspension is equipped with automatically operable wheel slip sensing and control means of known type while the non-drive tag or pusher axle suspension is provided with automatically operable means of known type for transferring weight from the tag or pusher axle suspension to the drive axle suspension.
Heretofore, tandem rear axle suspensions for trucks and truck-tractors have been available combining a drive axle suspension and a non-drive tag or pusher axle suspension having automatically operating wheel slip or spin sensing and control means for the drive axle suspension and automatically operable weight transfer means for the tag or pusher axle suspension. Furthermore, roll compliant, non-reactive drive axle suspensions have been available as well as roll stable non-drive tag or pusher axle suspensions of the rigid beam type. However, tandem rear axle suspensions have not been previously known or available combining a non-reactive, roll compliant drive axle suspension having a single axle with a roll stable non-drive tag or pusher axle suspension having a single axle of the rigid beam type, either with or without wheel slip sensing and control means or weight transfer means. Such novel combinations of non-reactive, roll compliant drive axle suspensions having single axles and roll stable tag or pusher axle suspensions having single axles of the rigid beam type are now provided in accordance with the present invention.
For a more complete understanding of the nature and scope of the invention reference may now be had to the following detailed description of a presently preferred embodiment of the invention taken with the accompanying drawings wherein: